1. Field of the Invention
This invention relates generally to expanding the capabilities of a computer system, and, more particularly, to interfacing an external module with a primary module of a computer system.
2. Description of the Related Art
Historically, computer systems are general purpose devices that may be modified to perform particular tasks or functions. Generally, computer systems include a motherboard mounted in a cabinet. The motherboard typically includes a number of connectors or slots in which special purpose printed circuit boards may be inserted. These special purpose printed circuit boards may be used to add to or enhance the functionality of the computer system. For example, a conventional computer system may have its graphics capability enhanced by the addition of a graphics card. Similarly, the sound-producing capability of the computer system may be enhanced by the addition of a sound card.
One limitation on the ability to add to or enhance the functionality of the computer system is the number of slots or connectors that are provided. For example, if a user desires to enhance both sound and graphics capability, but only a single slot or connector is available, then the user must select the more desirable function or alternate between the cards, as needed. Neither solution is particularly desirable.
In some computer systems, additional functionality is provided on the motherboard itself. That is, the motherboard may be designed with electrical leads or traces formed therein to provide interconnectivity to a special-purpose circuit. The integrated circuits used to perform the functionality of the special-purpose circuit may only be included on select motherboards where the customer has ordered the special-purpose circuit. Typically, this approach is used so that a manufacturer may design a single motherboard that is used in a variety of computer systems to achieve economies of scale in manufacturing the motherboard. However, the real estate on the motherboard is “wasted” in those computer systems that do not use the special purpose circuit. For example, it may be desirable to have additional microprocessors to provide a high-end computer system capable of performing more intense processing in some applications. Thus, the motherboard may be designed to accept multiple microprocessors, but only a single microprocessor is actually placed in the motherboard unless the customer requests additional microprocessors. Thus, in those systems in which only a single microprocessor is installed, valuable motherboard real estate is unused and performing no useful work for the computer system.
Some prior devices have suggested adding or enhancing functionality through an external connection to the computer system. This solution suffers from a variety of mechanical and electrical challenges, such as providing secure and high-quality electrical connections, difficulty of assembly, electromagnetic interference, cooling, and the like. Additionally, for these external or secondary devices to operate efficiently, they need to have a high-speed connection to the computer system, such as through a peripheral component interface (PCI) bus, an industry standard architecture (ISA) bus, a proprietary bus, a system bus, or the like. Extending a high-speed bus external to the cabinet of the computer system can create substantial difficulties. For example, a high-speed bus is sensitive to the length of the traces used to form the bus. Extending the bus will, of course, change the length of the traces, creating the potential for reflections and other interference anomalies on the extended bus. Further, timing difficulties may also arise from the extended distance that the signals must travel on the extended bus.
While minimizing the length of the high-speed bus extension is helpful in minimizing these electrical problems, it creates problems for physically connecting the components of the computer system to one another. For example, if the components to be interconnected are not physically aligned, a connection between the components may be impossible. If a connection can be physically accomplished, forces acting on the components due to misalignment may result in mechanical failure of one or more of the components, either immediately or at some future time. Such stress in these components can cause traces to crack and fail, solder joints to become loosened, and board-level devices to fail.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.